Phase shift mask blank having a coated central shading pattern and uncoated peripheral portion

ABSTRACT

In a method and an apparatus for processing, by the use of a processing solution, a substrate which has a principal surface divided into an unprocessing region and a processing region surrounding the unprocessing region, a guide member has an end portion which is faced with the processing region with a gap left between the processing region and the end portion and with an inside space left between the unprocessing region and the guide member. The processing solution is supplied to and kept in the gap due to capillarity and surface tension of the processing solution without being spread onto the unprocessing region. Thus, the processing region alone is processed by the processing solution. When the principal surface is supported by the guide member, the processing solution may be given from a back surface of the substrate to the gap through a side gap formed between the guide member and the substrate. Alternatively, when the guide member is covered over the principal surface of the substrate with the back surface of the substrate supported on a support member, the processing solution is fed onto the guide member and sent into the gap through via holes formed on the end surface of the guide member. The processing solution may be either a solvent or a resist solution. The substrate may serve to form a phase shift mask blank, a reticle testing substrate, or the like.

This is a divisional of copending application(s) Ser. No. 08/128,541filed on Sep. 28, 1993, now U.S. Pat. No. 5,474,807.

BACKGROUND OF THE INVENTION

This invention relates to a method and an apparatus for use inprocessing a substrate to remove or form a film on a processing regionof the substrate. It should be noted throughout the instantspecification that the method and the apparatus are used inmanufacturing a photomask, a photomask blank, a reticle, a reticleblank, a reticle testing substrate, a semiconductor substrate, amagnetic disk, a color filter, and the like, although description willbe mainly made about the photomask blank and the reticle testingsubstrate.

Recent requirements have been directed to a photomask blank which candelineate a fine pattern at a high precision and a high resolution bythe use of a photolithography technique. To this end, a phase shiftmethod has been proposed in Japanese Unexamined Patent Publication Sho58-173744. With this method, it is possible to manufacture a phase shiftphotomask blank which comprises a transparent substrate, a plurality ofopaque patterns on the substrate, and a transparent film on thesubstrate and the patterns. The transparent film is selectively etchedinto transparent patterns by a photolithography technique to manufacturethe phase shift photomask.

Herein, the transparent film is formed by a spin coating technique inconsideration of flatness of the transparent film. A flat transparentfilm is produced by the use of the spin coating technique at a centerportion of the transparent film and may be, for example, a resist film.However, the flatness of the transparent film is not kept at aperipheral portion of the film because the transparent film tends tobecome thick at the peripheral portion due to the spin coatingtechnique, as known in the art. In other words, the peripheral portionof the transparent film has an irregular thickness when the spin coatingtechnique is used to form the transparent film.

Moreover, the periphery of the phase shift photomask is intended to beattached or supported by other equipment, such as a support member whenoptically coupled to an optical system for the photolithography. Thismeans that the periphery of the phase shift photomask is preferably flatas, otherwise, optical adjustment of the phase shift photomask becomesdifficult because of the irregular thickness of the peripheral portionof the transparent film.

In order to avoid the irregular thickness of the peripheral portion,disclosure is made in Japanese Patent Publication No. Sho 58-19350, forremoving the transparent film at the peripheral portion thereof from thesubstrate. More specifically, a solvent for the transparent film isdischarged from a nozzle onto the peripheral portion of the transparentfilm. However, the solvent is not confined only to the peripheralportion of the transparent film. In this case, the peripheral portion ofthe transparent film is referred to as a processing region while theremaining portion is an unprocessing region. With this method, thesolvent undesirably spreads from the processing region to theunprocessing region. As a result, the unprocessing region of thetransparent film is often dissolved by the solvent in addition to theprocessing region.

Alternatively, a reticle testing substrate is used for optically testinga reticle which has a pattern on a reticle surface. In other words, thereticle testing substrate serves to determine whether or not a failureis included in the pattern on the reticle. To this end, such a reticletesting substrate comprises a quartz substrate having a substratesurface, an opaque film of chromium deposited on a peripheral region ofthe substrate surface, and a resist film uniformly coated on thesubstrate surface and the opaque film. In this situation, the pattern onthe reticle surface is optically transcribed onto the resist film coatedon the substrate surface of the reticle testing substrate by the use ofa step and repeat technique. Such optical transcription of a pattern iscarried out by adjusting a focus of an optical system to the opaquefilm. Thus, a resist pattern is formed on the substrate surface and isidentical with the pattern on the reticle to be tested.

Under the circumstances, light is emitted onto the resist patternthrough the reticle testing substrate so as to form a pattern image ofthe resist pattern by the light and to check whether or not a failure isincluded in the pattern image. When a failure is found on the patternimage, the reticle which corresponds to the reticle testing substrate isrejected as a faulty reticle and, otherwise, the reticle is accepted asa non-faulty reticle.

Herein, it is to be noted that the opaque film of chromium is left onlyalong the periphery of the quartz substrate and may not be alwaysprecise in size. In order to leave the opaque film only along theperiphery of the quartz substrate, a chromium film is deposited on thequartz substrate and the photoresist layer is left only on a peripheralportion of the chromium film. Thereafter, the chromium film is etched byan etchant to leave the opaque film along the periphery of the quartzsubstrate. In this way, it is very simple to leave the photoresist filmonly along the peripheral portion, namely, the processing region of thechromium film.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a method of processing asubstrate, which is capable of readily and accurately processing only aprocessing region on the substrate by the use of a processing solution.

It is another object of this invention to provide a method of the typedescribed, which is capable of removing superfluous film in theprocessing region by a solvent used as the processing solution.

It is still another object of this invention to provide a method of thetype described, which is capable of forming a desirable film only in theprocessing region.

It is yet another object of this invention to provide an apparatus whichis capable of effectively processing only a processing region by the useof a processing solution.

It is another object of this invention to provide an apparatus of thetype described, which is capable of desirably removing superfluous filmonly in the processing region by the solvent.

It is another object of this invention to provide an apparatus of thetype described, which is capable of forming a desirable film only in theprocessing region.

It is a further object of this invention to provide a product, such as aphotomask blank, a reticle blank, which can be manufactured by theabove-mentioned method and apparatus.

A method according to an aspect of this invention is for use inprocessing, by the use of a processing solution, a substrate which has aprincipal surface divisible into an unprocessing region and a processingregion surrounding the unprocessing region. The method comprises thesteps of preparing a guide member having a bottom portion and anextended portion which is contiguous to the bottom portion and whichdefines an end portion corresponding to the processing region, locatingthe guide member and the substrate with a gap between the end portion ofthe guide member and the processing region of the substrate and with aninternal space between the unprocessing region and the bottom portionand which is wider than the gap, and supplying the processing solutionto the gap to process the processing region by the processing solutionwith the processing solution confined in the gap alone.

An apparatus according to another aspect of this invention to carry outthe method comprises a guide member having a bottom portion and anextended portion which is contiguous to the bottom portion and whichdefines an end portion corresponding to the processing region, a spacermember located between the guide member and the substrate with a gapbetween the end portion of the guide member and the processing region ofthe substrate and with an internal space between the unprocessing regionand the bottom portion and which is wider than the gap, and a solutionsupplying member for supplying the processing solution to the gap toprocess the processing region by the processing solution with theprocessing solution confined in the gap alone.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic sectional view of a conventional apparatus for usein removing an unnecessary film from a substrate;

FIG. 2 is a sectional view of an apparatus according to a firstembodiment of this invention;

FIG. 3 is a schematic sectional view for use in describing operation ofthe apparatus illustrated in FIG. 2;

FIG. 4 is a partial sectional view for use in describing a state of asubstrate processed by the apparatus illustrated in FIG. 2;

FIG. 5 is a partial sectional view for use in describing a processcarried out by the apparatus illustrated in FIG. 2;

FIG. 6 is a partial sectional view of an apparatus according to amodification of the first embodiment of this invention;

FIG. 7 is a similar view of an apparatus according to anothermodification of the first embodiment of this invention;

FIG. 8 is a sectional view of an apparatus according to a secondembodiment of this invention;

FIG. 9 is a plan view of a guide member for use in the apparatusillustrated in FIG. 8;

FIG. 10 is a partial sectional view for use in describing a processcarried out by the apparatus illustrated in FIG. 8;

FIG. 11 is a similar view for use in describing another process carriedout by the apparatus illustrated in FIG. 8;

FIG. 12 is a plan view for use in describing a phase shift mask blankmanufactured by the apparatus illustrated in FIG. 8;

FIG. 13 is a plan view of another guide member used in the apparatusillustrated in FIG. 8;

FIG. 14 is a plan view of a product manufactured by the use of the guidemember shown in FIG. 13; and

FIG. 15 is a partial sectional view of an apparatus according to amodification of the second embodiment illustrated in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, description will be directed to a conventionalmethod which is substantially equivalent to that mentioned in JapanesePatent Publication Sho 58-19350, described previously in the instantspecification. The conventional method is for use in manufacturing aphase shift photomask blank formed from a substrate block as shown inFIG. 1. In the illustrated example, the substrate block comprises atransparent substrate 21 having a principal or front surface directedupwards in FIG. 1, a plurality of opaque or shading films 22 on theprincipal surface, and a coated film 23 covering the principal surfaceand the opaque films 22. The principal surface is divided into anunprocessing or a center region located at a center portion of theprincipal surface and a processing or a peripheral region surroundingthe center portion. Thus, the processing region is placed at aperipheral portion of the principal surface.

The illustrated substrate block is supported by a turntable 24 and isrotated on the turntable 24 as indicated by an arrow. A nozzle 25 isdirected towards a peripheral region of a back surface opposite theprincipal surface of the substrate 21. Thus, the nozzle 25 is placedunder the substrate 21 in the example being illustrated.

It is assumed that the coated film 23 is coated by a spin coating methodand is therefore flat on the center portion of the principal surface andis irregularly thick or heaped at the peripheral region of the principalsurface. A solvent 26 is discharged through the nozzle 25 so as todissolve the coated film 23 in the processing region thereof and toremove the coated film 23 from the processing region, namely, theperipheral portion while the substrate block is rotated on the turntable24.

In this event, the solvent 26 travels along a side surface of thesubstrate 21 by surface tension and moves on the coated film 23 of theperipheral region of the principal surface. As a result, the coated film23 is dissolved at the peripheral region of the principal surface andthe side surface, as illustrated in FIG. 1. Thereafter, the solvent isblown off the substrate block by centrifugal force resulting from therotation of the block, as shown in FIG. 1. Thus, the processing regionof the coated film 23 is removed from the substrate 21.

With this method, it is difficult to determine conditions for removingonly the coated film 23 at the processing region. Consequently, thecoated film 23 in the unprocessing region is often removed, as pointedout previously in the instant specification.

Referring to FIG. 2, an apparatus according to a first embodiment ofthis invention is for use in manufacturing a phase shift photomask blankby removing a superfluous or an undesired coated film from a substrateblock. As in FIG. 1, the substrate block comprises a transparentsubstrate 21 of quartz glass which has a size of 6 (inches)×6(inches)×0.25 (inch) and a principal or front surface 21a directeddownwards of FIG. 2 and a back surface 21b opposite the principalsurface 21a. A plurality of opaque films or shading films 22 aredeposited on a center region of the principal surface 21a of thesubstrate 21 to form a shading pattern and are covered with a coatedfilm 23 which may be, a poly-siloxane SOG (Spin-On-Glass) film as knownin the art and which is assumed to be coated by spin coating in theillustrated example. The spin coating may be carried out by the use of acoating solution which includes silicon oxide and which may be, forexample, ACCUGLASS211S manufactured and sold by Allied Signal CompanyLtd.

Referring to FIGS. 3 and 4 together with FIG. 2, the coated film 23extends over the entire principal surface 21a and may extend on a sidesurface 21c of the substrate 21 and the back surface 21b of thesubstrate 21. In FIGS. 3 and 4, the coated film 23 is on the principalsurface 21a and both the side and the back surfaces 21c and 21b. Thecoated film 23 has a thickness of about 4,000 angstroms at the centerregion and is formed by spin coating the above-mentioned coatingsolution at a rotation speed of 1,000 rpm for ten seconds.

As illustrated in FIGS. 3 and 4, the coated film 23 has a flat oruniform portion 23a at the center region of the substrate 21, a heapedup portion 23b at the peripheral region 21d of the substrate 21, a sideportion 23c on the side surface 21c of the substrate 21, and a backportion 23d on the back surface 21b of the substrate 21. Thus, thecoated film 23 is flat in the center region of the principal surface 21aand is uneven on the peripheral region 21d surrounding the centralsurface of the substrate 21. In other words, the spin coating tends toundesirably form the heaped up portion 23b at the peripheral region 21dof the substrate 21, as pointed out in conjunction with FIG. 1. The backportion 23d is also heaped up on the back surface 21b as on theperipheral portion 21d of the substrate 21.

In the illustrated example, the coated film 23 on the peripheral region21d is removed or processed together with the coated film 23 of both theside surface 21c and the back surface 21b in a manner similar to thespin coating. In this connection, the peripheral portion 21d and thecenter region of the principal surface will be referred to as aprocessing region and an unprocessing region, respectively.

The apparatus shown in FIG. 2 serves to remove the heaped up portion23b, the side portion 23c and the back portion 23d by the use of asolvent which can dissolve the coated film 23 and which may be, forexample, acetone.

The illustrated apparatus comprises a guide member 31 of cup shape whichis rotatable with a rotation axle 32. The rotation axle 32 ismechanically coupled to a motor or the like (not shown) and can berotated at a rotation speed determined by the motor. The guide member 31has a bottom section 31a fixed to the rotation axle 32, an extendedportion 31b contiguous to the bottom section 31a and offset from thebottom portion 31a, and a wall portion 31c extending upright from theextended portion 31b. The wall portion 31c is contiguous to an externalportion 31d disposed horizontally outside of the wall portion 31c. Inthe example being illustrated, the extended portion 31b defines an endportion which is offset upwards in FIG. 2 and which faces the peripheralregion 21d of the principal surface 21a in a manner to be describedlater in detail.

As shown in FIGS. 3 through 5, a block setting zone is formed within theguide member 31 to locate the substrate block and is defined by thebottom portion 31a, the extended portion 31b, and the wall portion 31c.The block setting zone serves to keep the substrate block substantiallyhorizontal and therefore has a size which can accommodate the substrateblock in the block setting zone.

In addition, a plurality of nylon threads 36a each of which is 0.1millimeter thick are arranged on the extended portion 31b, with a top ofeach nylon thread 36a projecting upwards, as shown in FIG. 2. Each ofthe nylon threads 36a forms a loop or a ring, as illustrated in FIG. 2,and is called a nylon ring. The nylon rings 36a may be positioned with aspacing between two adjacent nylon rings 36a and the nylon rings serveas spacers between the extended portion 31b and the substrate block, aswill later be described. In the illustrated example, the nylon rings 36aare equal in number to eight.

Moreover, a plurality of additional nylon threads 36b are also arrangedat the external portion 31d and the wall portion 31c. Each of the nylonthreads 36b is formed as a loop and is called a nylon loop. Theadditional nylon loops 36b are arranged so that each additional nylonloop 36b surrounds the wall portion 31c as shown in FIG. 2. Eachadditional nylon loop 36b serves as an additional spacer between theside surface 21c of the substrate 21 and the wall portion 31c andsixteen nylon loops 36b are employed in the illustrated example. Everyother one of the additional nylon threads 36b has a thickness or adiameter of about 0.44 millimeter while each of the remaining additionalnylon threads 36b has a thickness or a diameter of about 0.21millimeter. The thinner nylon threads also serve to cause the solvent toflow smoothly along the thin nylon threads and, as a result, to guidethe solvent as will become clear later.

A nozzle 40 is opposite the guide member 31 and is perpendicular to thebottom portion 31a of the guide member 31. The solvent is sprayedthrough the nozzle 40 downwards in FIGS. 2 through 5, as depicted at 41in FIG. 2.

In operation, the substrate block is set in the block setting zone ofthe guide member 31 illustrated in FIGS. 2 through 5, with the principalsurface 21a of the substrate 21 directed downwards in FIGS. 2 through 5.In this situation, the nylon rings 36a are brought into contact with theheaped up portion 23b of the coated film 23 formed on the peripheralregion 21d of the substrate 21. Thereby the substrate block is keptsubstantially horizontal with a gap left between the extended portion31b of the guide member 31 and the coated film 23 on the substrate 21.The gap is determined by the thickness or a diameter of each of thenylon threads 36a. The gap may have a size of about 0.17 millimeter.Likewise, the substrate block is spaced from the wall portion 31c withinthe block setting zone by a side gap determined by the additional nylonloops 36b, as shown in FIG. 2. The side gap may have a width of 0.44millimeter.

Thus, the peripheral region 21d of the substrate 21 faces the extendedportion 31b of the guide member 31 with the gap left therebetween. Onthe other hand, the center region 21a of the substrate 21 faces thebottom portion 31a of the guide member 31 at an internal spacing whichis wider than the gap, as readily understood from FIGS. 2 through 5. Inother words, the processing region and the unprocessing region of thesubstrate 21 are opposed the extended portion 31b and the bottom portion31a respectively of the guide member 31 through the gap and the internalspacing, respectively.

At first, the guide member 31 is rotated at a first rotation speed of 50rpm. During the rotation of the guide member 31, the solvent, forexample, acetone, is sprayed in an amount of 25 milliliters from thenozzle 40 towards the back surface 21b of the substrate 21, as shown inFIG. 2. During this process, the solvent is caused to flow from the backsurface 21b of the substrate 21 along the side portion 23c of the coatedfilm 23 to the peripheral portion 23b of the coated film 23. On theperipheral portion 23b of the coated film 23, the solvent travels bycapillarity towards the center region 21a of the substrate 21 throughthe gap defined by the nylon rings 36a.

When the solvent has reached an offset portion, namely, a boundarybetween the extended portion 31b and the bottom portion 31a of the guidemember 31, the solvent stops due to the surface tension of the solvent.Therefore, the solvent does not travel to the center region 21a, namely,the unprocessing region of the substrate 21. Consequently, the coatedfilm 23 is not removed by the solvent at the center region 21a of thesubstrate 21. On the other hand, the back portion 23d and the sideportion 23c of the coated film 23 are contacted by the solvent togetherwith the peripheral portion 23b, which causes dissolution reaction tooccur between the solvent and the coated film 23. The dissolutionreaction brings about dissolving of the coated film 21 by the solventand removal of the coated film 21 at the peripheral, side, and backportions 23b, 23c, and 23d. Thus, the coated film 23 is dissolved onlyat the processing region of the substrate 21 and not at the unprocessingregion of the substrate 21.

After the dissolving action is finished between the solvent and thecoated film 23, the guide member 31 is rotated at a high or a secondrotation speed of 1500 rpm for one second. During this high speedrotation, the dissolved coated film is scattered outside the substrateblock. Thus, unnecessary films coating at the peripheral region, theside surface 21c, and the back surface 21b are removed from thesubstrate 21. Herein, it is to be noted that the above-mentioned solventscattering process should be completed before the volatile solvent hasthickened.

In order to thoroughly remove the unnecessary coated film, dissolving iscarried out at a third rotation speed of 70 rpm for ten seconds afterthe solvent scattering process. Subsequently, dissolving is carried outat a fourth rotation speed of 100 rpm for ten seconds and this isfollowed by a drying and scattering process carried out at a fifthrotation speed of 1500 rpm for ten seconds. The substrate block is thusconverted into the phase shift mask blank by removal of the unnecessarycoated film.

Finally, rotation of the guide member 31 is stopped and the phase shiftmask blank is taken out of the guide member 31. The phase shift maskblank manufactured in the above-mentioned manner comprises a phase shiftfilm which is composed of the coated film and which is left in a squareshape on the center region of the substrate 21.

The solvent may be replaced by methanol, isopropyl alcohol, or the like.

In FIG. 5, the side gap between the wall portion 31c of the guide memberthe side surface 21c of the substrate 21 is assumed to be equal in widthto 0.44 millimeter in the above-mentioned example. However, the side gapmay have a gap width such that the solvent 41 can flow through the sidegap along the side surface 21c of the substrate 21 towards theperipheral region 21a.

In addition, although the gap between the extended portion 31b of theguide member 31 and the peripheral region 21d of the substrate 21 isassumed to be equal to 0.17 millimeter, the size or width of the gap maybe determined in consideration of the viscosity of the solvent so thatthe solvent can flow into the gap and can be held within the gap by thesurface tension of the solvent. Furthermore, the gap need not have auniform width but may be gradually tapered from the outer periphery ofthe substrate 21 towards the center region of the substrate 21. In thelatter case, the gap gradually narrows as the gap approaches the centerregion of the substrate 21. With this construction the solvent can bereadily introduced into the gap.

In the above-mentioned method, the guide member 31 is rotated so as todissolve the coated film 23 and to scatter the solvent which dissolvedthe coated film 23. Although such rotation processes are alternatelyrepeated three times for each of the dissolving and the scattering stepsin the above-mentioned example, the rotation processes may be carriedout at least one time for each of the dissolving and the scatteringoperations. The rotation speed and the rotation time may be optionallyselected in consideration of the solvent used, the thickness of thecoated film 23, and the like.

In practice, the method illustrated with reference to FIGS. 2 through 5has been applied to removal of the heaped up portion 23b of the coatedfilm which provides a maximum thickness of about 1.6 micronmeters at aposition about 10 millimeters from the outer periphery of the substrate21 and a thickness of about 0.3 micronmeter at a position 21 millimetersfrom the outer periphery of the substrate 21. In this case, the coatedfilm 23 has been removed over a width of about 20.0 millimeters from theouter periphery of the substrate 21. Stated otherwise, the heaped upportion 23b of about 20.0 millimeters has been removed in a rectangularshape from the peripheral region 21d of the substrate 21. As a result,the remaining coated film 23 has a thickness of about 0.3 micronmeter ata position about 21 millimeters from the outer periphery of thesubstrate 21. It has been found that the coated film 23 which is about0.3 micronmeter thick has no cracks therein and is very convenient forthe phase shift mask blank.

Thus, the phase shift mask blank retains the coated film 23 except forthe peripheral region 21d, the side surface 21c, and the back surface21b. With this mask blank, it is possible to prevent adherence of anydust to the back and the side surfaces 21c and 21b of the substrate 21and to therefore keep the phase shift mask blank clean. Moreover, thephase shift mask blank can be accurately attached to an exposure deviceor other optical device by mounting the peripheral region 21d onto suchan exposure device.

Referring to FIG. 6, an apparatus according to a modification of thefirst embodiment illustrated in FIGS. 2 through 5 further comprises athrough hole 44 formed in the extended portion 31b of the guide member31 and an additional nozzle 45 which is placed under the guide member 45and which faces the through hole 44. The guide member 31 has an internalside surface defining the through hole 44.

In the illustrated example, the solvent 41 is discharged from the nozzle40 placed over the substrate 21 and is simultaneously discharged fromthe additional nozzle 45. With this structure, the superfluous coatedfilm is very quickly removed from the substrate 21, which is helpful tomanufacture the phase shift mask blank at a high speed in comparisonwith the method illustrated in conjunction with FIGS. 2 through 5.

Referring to FIG. 7, an apparatus according to another modification ofthe first embodiment illustrated in FIGS. 2 through 5 comprises noadditional nozzle 45, although the through hole 44 is formed through theguide member 31. In this case, the through hole 44 serves to dischargeunnecessary solvent therethrough. The discharge of the unnecessarysolvent can be smoothly carried out when a thread or a needle isinserted in the through hole 44.

The nylon threads 36a and 36b which act as spacers may be replaced byprojections formed by screws or tapes which are composed of a materialinsoluble in the solvent.

Referring to FIG. 8, an apparatus according to a second embodiment ofthis invention is shown for manufacturing a phase shift mask blank byremoving superfluous coated film from a substrate block, as in the firstembodiment. It is to be noted that the substrate block is directedupwards in FIG. 8, which differs from the apparatus illustrated in FIGS.2 through 7. In this connection, the substrate block comprises similarparts designated by like reference numerals. Specifically, the substrateblock comprises the substrate 21 of glass having the principal or frontsurface 21a directed upwards in FIG. 8, the back surface 21b directeddownwards in FIG. 8, and the side surface 21c contiguous to theprincipal and the back surfaces 21a and 21b. The principal surface 21ais divided into the center region and the peripheral region 21d.

A plurality of opaque or shading films 22 are selectively formed on theprincipal surface 21a and are covered with coated film 23 which extendsover the entire principal surface 21a and which may be, for example, apoly-siloxane spin-on-glass (SOG) film as in the first embodiment.

In practice, the illustrated substrate comprises the substrate of quartzglass having a size of 6 (inches)×6 (inches)×0.25 (inch), the shadingfilms 22 of chromium, and the coated film 23 of the poly-siloxane SOG.The shading films 22 are deposited at the center region of the principalsurface 21a and are not deposited at the peripheral region 21d. On theother hand, the coated film 23 is coated by spin coating and extendsfrom the center region of the principal surface 21a to the peripheralregion 21d. At the peripheral region 21d, the coated film 23 is heapedup as mentioned in conjunction with FIG. 4. Specifically, the spincoating has been carried out at a rotation speed of 1000 rpm for tenseconds. The resultant coated film 23 has a thickness of 4,000 angstromsin the center region, a thickness of 1.6 micronmeters at the heaped upportion, and a thickness of 0.3 micronmeter at a distance of 2.1millimeters from the outer periphery of the substrate block.

The apparatus shown in FIG. 8 comprises a support member 51 which issimilar in structure to the guide member 31 shown in FIGS. 2 through 7and which serves to support the back surface 21b of the substrate 21.The support member 51 is fixed to a rotation axle 52 mechanicallycoupled to a motor or the like and is rotated at a rotation speeddetermined by the motor. More particularly, the support member 51 has abottom part 51a of a dish shape in section, an extended part 51b offsetfrom the bottom part 51a with an offset part between the bottom part 51aand the extended part 51b, a wall part 51c extending upright from theextended part 51b, and an external part 51d extending horizontallyoutwards from the wall part 51c.

A plurality of nylon rings 53a are arranged on the extended part 51b sothat the top of each nylon ring 53a projects from the extended part 51b.In the illustrated example, the nylon rings 53a are equal in number toeight and are spaced from one another at the periphery of the extendedpart 51b and have individually a thickness or diameter of 0.15millimeter. Thus, the nylon rings 53a rest on the extended part 51b in amanner similar to the nylon rings 36a illustrated in FIG. 2. As readilyunderstood from FIG. 8, the bottom part 51a defines an inner spacesmaller in size than the size of the substrate block while the wall part51c defines an internal space somewhat greater in size than thesubstrate block. Accordingly, the substrate block can be accommodatedwithin the support member 51 in the illustrated manner.

The apparatus further comprises a guide member 55 which is operable in amanner similar to the guide member 31 mentioned in conjunction withFIGS. 2 through 7 and which is supported on the support member 51 sothat the substrate block is covered by the guide member 55. Morespecifically, the guide member 55 has a cup shape in section as in FIGS.2 through 7 but is upset relative to that illustrated in FIGS. 2 through7. Thus, the illustrated guide member 55 covers the substrate block andis referred to as a cover member.

The guide member 55 has an outer configuration substantiallycorresponding to that of the support member 51 and is of a square shapein the illustrated example. The guide member 55 further has a baseportion 61 directed upwards in FIG. 8 and a wall portion 62 whichextends downwards in FIG. 8 from the base portion 61 and which definesan inside space therein. In any event, the guide member 55 has a cupshape in section while the inside space has a square shape.

The base portion 61 operates similarly to the bottom portion 31a of theguide member 31 shown in FIGS. 2 through 7 and is called a bottomportion. The base portion 61 of FIG. 8 has a base surface 61 a directedupwards in FIG. 8 and an inside surface 61b directed downwards. The wallportion 62 has a wall end surface 62a which is directed downwards inFIG. 8 and which faces the principal surface of the substrate 21. Theinside space is defined by the inside surface 61b and the wall portion62.

As readily understood from FIG. 8, the wall end surface 62a of the guidemember 55 covers the peripheral region of the principal surface of thesubstrate 21 while the inside surface 61b is opposite a center region ofthe principal surface of the substrate 21. Thus, the wall end surface62a faces a processing region of the substrate 21 while the insidesurface 61b faces the region of the substrate 21 not to be processed, asin the guide member 31 shown in FIGS. 2 to 7. In the illustratedexample, the difference in height between the inside surface 61b and thewall end surface 62a is equal to 1.5 millimeters while the peripheralregion of the substrate 21 is spaced by a distance of about 20millimeters from the wall portion 62.

Referring to FIG. 9 in addition to FIG. 8, the guide member 55 has aninside surface of square shape surrounded by the wall end surface 62a.At the wall end surface 62a, a number of holes 63 are formed along aninside edge of the wall end surface 62a and the holes 63 are spaced fromone another at a predetermined distance. In addition, the guide member55 has four projected portions and four openings 64 formed in theprojected portions. In FIG. 9, the projected portions are placed in acenter region of each outer side edge of the wall end surface 62a. Theopenings 64 serve to insert positioning pins 65 (FIG. 8) and to fastenthe guide member 55 to the support member 51, as shown in FIG. 8.Consequently, the guide member 55 can be rotated around the rotationaxle 52 together with the support member 51 and the substrate block.

Moreover, four nylon loops or rings 66 are disposed at positionsradially inwards of the openings 64. Each of the nylon rings 66partially protrudes at the wall end surface 62a and the base surface61a, as depicted at FIG. 8. The nylon rings 66 protruding at the wallend surface 62a serve as spacers which keep a gap between the guidemember 55 and the substrate 21, as for the nylon rings 36a shown in FIG.2. In the illustrated example, the nylon thread used for each of thenylon rings 66 has a thickness or a diameter of about 0.15 millimeter.As a result, the gap between the wall end surface 62a and the substrateblock is kept at 0.15 millimeter while the space between the substrateblock and the inside surface 61b of the guide member 55 becomes equal to1.65 millimeters.

Turning back to FIG. 8, the nozzle 40 is placed over the guide member 55to discharge the solvent 41 at a preselected speed onto the base surface61a of the guide member 55. Thus, the nozzle 40 illustrated in FIG. 8faces the base surface 61a of the guide member 55 and is connected to asolvent feeder (not shown) for feeding the solvent 41 to the nozzle 40.The solvent 41 may be, for example, acetone or the like when the coatedfilm 23 is formed by poly-siloxane SOG.

Referring to FIG. 8 again and to FIGS. 10 and 11, the coated film 23 ofthe poly-siloxane SOG covers the shading films 22 and the principalsurface 21a of the substrate 21 by the use of spin coating to form thesubstrate block illustrated in FIG. 10. The substrate block is set onthe apparatus as shown in FIG. 8 with the principal surface 21a of thesubstrate 21 directed upwards in FIG. 8. Hence the substrate 21 is notinverted, which is different from FIGS. 2 through 7. Therefore, theapparatus of FIG. 8 is more effective in handling the substrate incomparison with that shown in FIGS. 2 through 7.

Next, the guide member 55 covers the substrate block and is fixed to thesupport member 51 by the positioning pins 65. In this event, the guidemember 55 covers the peripheral region 21d of the principal surface 21awith the gap of 0.15 millimeter between the coated film 23 and the wallend surface 62a, as best shown in FIG. 10 and with the inside space of1.65 millimeters between the inside surface 61a and the substrate block.As mentioned before, the nylon rings 66 serve to preserve the gapbetween the coated film 23 and the wall end surface 62a. It is assumedthat the guide member 55 covers the peripheral region 21d of a width of20 millimeters. In addition, a side gap is also left between the outerperiphery of the substrate 21 and the wall part 51c of the supportmember 51.

In this condition, the solvent 41 is discharged from of the nozzle 40 toremove the coated film 23 on the peripheral region 21d of the substrateand to consequently manufacture the phase shift mask blank which has anuncovered area on the peripheral region 21d of the substrate 21.Specifically, acetone in an amount of about 25 millimeters is suppliedas the solvent 41 through the nozzle 40 while the support member 51 isrotated together with the substrate block and the guide member 55 at arotation speed of 200 rpm for about 15 seconds. During this process, thesolvent 41 is caused to flow through the holes 63 downwards in FIG. 8from the base surface 61a of the guide member 55 and into the gapbetween the substrate block and the wall end surface 62a. Thereafter,the solvent 41 quickly travels outwards of the substrate block due tothe capillarity and the centrifugal force resulting from the rotation ofthe support member 51, as illustrated in FIG. 10. The solvent 41 alsopasses through the side gap between the support member 51 and thesubstrate block to be brought into contact with the side surface 21c andthe back surface 21b of the substrate 21.

As a result, the coated film 23 is removed from the peripheral region21d, the side surface 21c, and the back surface 21b of the substrate 21by the solvent 41 in the manner described with reference to FIGS. 2through 7.

On the other hand, the solvent 41 does not pass towards the centerregion of the principal surface 21a of the substrate 21 due to thesurface tension of the solvent 41, as shown in FIG. 9. This is becausethe inside space between the substrate block and the inside surface 61bof the guide member 55 is very much greater than the gap between thesubstrate block and the wall end surface 62a.

Thus, the coated film 23 is dissolved by the solvent 41 at theperipheral region 21d of the substrate 21, namely, the processing regionand is not dissolved at the center or the unprocessing region of thesubstrate 21, as best shown in FIG. 11.

After the above-mentioned reaction is finished for dissolving the coatedfilm 21 by the solvent 41, the support member 51 is rotated again at therotation speed of 200 rpm for about 20 seconds together with thesubstrate block and the guide member 55 with supply of the solventstopped. During this rotation of the support member 51, the solvent isscattered outwards, as symbolized by arrows in FIG. 8, and theunnecessary coated film is removed from the substrate 21. Herein, such ascattering process of the solvent 41 should be made before the viscosityof the solvent 41 becomes undesirably high due to volatilization of thesolvent 41.

Subsequently, the support member 51 is further rotated at the rotationspeed of 400 rpm for 10 seconds together with the substrate 21 and theguide member 55 so as to thoroughly carry out the removal of theunnecessary coated film and to dry the substrate 21. Thereafter, therotation of the support member 51 is stopped. Then, the substrate blockfrom which the coated film 23 is removed at the peripheral region 21d ofthe substrate 21 is separated from the apparatus illustrated in FIG. 8and is subsequently baked to convert the coated film 23 to a phase shiftfilm. Thus, the substrate block becomes the phase shift mask blank.

Referring to FIG. 12, the phase shift mask blank manufactured in theabove-mentioned apparatus and manner has the phase shift film 23 left inthe center region of the substrate 21 and at the peripheral region 21dit is uncovered. The uncovered peripheral region 21d has a width ofabout 20 millimeters and forms a processed region. Thus, when the heapedup portion 23b has the maximum thickness of about 1.6 micronmeters and athickness of 0.3 micronmeter at a position 20.5 millimeters from theouter periphery of the substrate blank before the above-mentionedprocess is carried out by the use of the above-mentioned apparatus, themaximum thickness portion is completely removed from the phase shiftfilm 23 which has a thickness of about 0.3 micronmeter at the edgeportion thereof. The peripheral region 21d is completely flat becausethe coated film 23 is thoroughly removed from the peripheral region 21d.With this structure, no cracking takes place in the phase shift film 23because the phase shift film 23 is only 0.3 micronmeter thick.

Furthermore, the solvent 41 smoothly and reliably travels through thegap between the wall end surface 62a and the substrate block due tocapillarity. However, the solvent 41 does not pass to the unprocessingor center region of the principal surface 21a because no influence takesplace due to wind force resulting from the rotation. Therefore, theprocessing region, namely, the peripheral region 21d alone is accuratelyprocessed or removed by the solvent 41.

Referring to FIGS. 13 and 14, an apparatus according to a modificationof the second embodiment of this invention comprises a guide member 55aillustrated in FIG. 13. As shown in FIG. 13, the guide member 55a has awall end surface 62a which covers not only the peripheral region 21d ofthe substrate 21 but also the center region of the substrate 21 in acrisscross manner. In other words, the inside surface 61b of the guidemember 55a is divided into four square surfaces 61b' each of which issurrounded by the wall end surface 62a, as illustrated in FIG. 14. Inthe wall end surface 62a, a number of holes 63 are arranged so that eachof the square surface 61b' is surrounded by a line of the holes 63. Inaddition, the openings 64 are provided in the projected portions of theguide member 55a as in the guide member 55 shown in FIG. 9 to fix theguide member 55a to the support member 51 by the positioning pins 65(FIG. 8). The nylon rings 66 are placed in the vicinity of the openings64 as in FIG. 8.

The guide member 55a shown in FIG. 13 is set into the apparatus of FIG.8 in a manner similar to the guide member 55 to process the substrateblock with the gap left between the wall end surface 62a and thesubstrate block. The solvent 41 is discharged from the nozzle 40 ontothe guide member 55a to be supplied through the holes 63 onto thesubstrate block. The solvent 41 passes through the gap over the wall endsurface 62a of the guide member 55a and is maintained within the gap. Onsupply of the solvent 41, the support member 51 may be rotated in amanner similar to that illustrated in conjunction with FIGS. 8 through11 or it may not be rotated.

At any rate, the phase shift mask blank shown in FIG. 14 is manufacturedby the above-mentioned process. In FIG. 14, the phase shift mask blankhas four partial phase shift films 23a to 23d left on the substrate 21with the remaining parts uncovered or exposed.

Referring to FIG. 15, another apparatus according to a modification ofthe second embodiment of this invention comprises a support member 51'somewhat modified from that illustrated in FIG. 8. Specifically, thesupport member 51' has a bottom part 51a, an extended part 51b, a wallpart 51c, and an external part 51d as in FIG. 8. The extended part 51bis offset from the bottom part 51a and has an opening 71 formed throughthe extended part 51b. The opening 71 serves to discharge superfluoussolvent 41 which is supplied to the back surface 21b of the substrate21. In this case, a guide thread or needle (not shown) may be suspendedfrom the opening 71 so as to smoothly guide the superfluous solvent 41and discharge the same.

Although the above description has been made only with reference to thephase shift mask blank, this invention may be also applied either toremoval of an unnecessary resist film on manufacturing a photomask, aphotomask blank, a semiconductor substrate, and the like or to theremoval of an insulating film deposited on an electrode portion formedon a display substrate.

To the contrary, this invention may be used for forming a coated film ona substrate. More particularly, assume the apparatus illustrated inFIGS. 2 or 8 is used for manufacturing a reticle testing substrate whichcomprises a quartz substrate, an opaque film of chromium deposited on aperipheral region of the quartz substrate, and a resist film coated on acenter region of the quartz substrate and the opaque film. In thisevent, the opaque film is deposited on the entire surface of thesubstrate to be etched from the center region of the quartz substrateand is left only on the peripheral region of the quartz substrate.Before etching the opaque film from the center region, a photo resistfilm is formed or left only on the peripheral region of the quartzsubstrate. Such a photo resist film must be deposited on the entireopaque film and thereafter selectively exposed to leave the photo resistfilm only on the peripheral region.

However, such a photo resist film can be selectively formed on theperipheral region of the quartz substrate directly by the use of theapparatus according to this invention. To this end, the guide member 31or 51 covers the center region of the quartz substrate after the opaquefilm is deposited over the entire principal surface. In this situation,the guide member is opposed to the opaque film formed on the peripheralregion of the quartz substrate with the gap left between the guidemember and the opaque film. The gap is extended on the peripheral regionof the quartz substrate. A resist solution is discharged from the nozzleto flow to the gap and be kept within the gap. Consequently, a resistfilm is formed on the opaque film only on the peripheral region of thequartz substrate. Thus, the resist film can be formed only on adesirable region by the use of the apparatus according to thisinvention. In this connection, the resist solution and the solvent maybe collectively called a processing solution.

Likewise, this invention may be used either for forming a protectionfilm on manufacturing a magnetic disk or for forming a protection filmon manufacturing a color filter.

Stated otherwise, this invention is effective to process a substrate bythe use of a solution which may either remove a film or form a film. Inaddition, such a film processed by this invention may be formed bysputtering, chemical vapor deposition (CVD), ion plating, evaporation,or the like.

While this invention has thus far been described in conjunction with afew embodiments thereof, it will be readily understood for those skilledin the art to put this invention into practice in various other ways.For example, removal of the poly-siloxane SOG film may be made by theuse of methanol, isopropyl alcohol while removal of the resist film maybe made by the use of a ketone, ester, aromatic hydrocarbon, hydrocarbonhalide, ether, or the like.

In the second embodiment illustrated in FIGS. 8 through 14, the holes 63may be moved on the wall end surface 62a outwards in FIG. 8. However, itis preferable that the holes 63 be adjacent to an inner edge of the wallend surface 62a because the solvent 41 is caused to flow in an outwarddirection. Two lines of the holes 63 may be arranged on the wall endsurface 62a instead of a single line of holes 63. With this structure,it is possible to protect the solvent 41 from being dried and left on anouter peripheral region of the substrate 21.

The gap between the wall end surface and the substrate block need not berestricted to 0.15 millimeter but may be selected in consideration ofthe viscosity of the solvent. In addition, the gap need not be uniformbut may be changed within a range in which capillarity takes place.Various kinds of spacers may be used in lieu of the nylon rings.

Moreover, the guide member 55 illustrated in FIG. 8 may have a pyramidalshape in section, as shown in Japanese Patent Publication No. Sho58-19350 or it may have a dome shape in section. Finally, the substrateto be processed may be circular, triangular, rectangular, polygonal, orthe like.

What is claimed is:
 1. A phase shift mask blank comprising:a substratewhich has a principal surface divided into a central portion and aperipheral portion surrounding the central portion; an opaque film onthe central portion; and a coated film on said substrate, said coatedfilm being on the central portion and covering said opaque film, andbeing removed from the peripheral portion by a processing solution whichis a solvent for said coated film, said processing solution beingsupplied through a gap, formed between said substrate and a guide memberadjacent to said substrate, onto the peripheral portion which is exposedin said gap while the substrate is rotated, to produce capillarity andcentrifugal force to be developed on said solution in the gap, saidsolvent being confined in said gap to said peripheral portion by saidcapillarity and said centrifugal force whereby only the coated film atsaid peripheral portion is dissolved by said solvent.
 2. A phase shiftmask blank as claimed in claim 1, wherein the substrate is rectangularand the coated film is also substantially rectangular and is operable asa phase shift film.
 3. A phase shift mask blank as claimed in claim 2,wherein the rectangular phase shift film is divided into a plurality ofrectangular partial phase shift films.
 4. A phase shift mask blank asclaimed in claim 1, wherein the coated film is a poly-siloxane SOG film.5. A phase shift mask blank comprising:a substrate which has a principalsurface divided into a central portion, and a peripheral portionsurrounding the central portion; an opaque film on the central portion;and a coated film on said substrate, said coated film being on thecentral portion and covering said opaque film, and being removed fromthe peripheral portion by supplying a processing solution onto theperipheral portion by a method comprising:positioning a guide member inadjacent facing relation to the principal surface of the substrate,providing said guide member with a central portion and a raisedperipheral portion offset from said central portion, locating the guidemember adjacent to the principal surface of the substrate such that thecentral portion of the guide member faces the central portion of thesubstrate while said peripheral portion of the guide member faces saidperipheral portion of the substrate, said peripheral portion of theguide member forming a gap with the peripheral portion of the substratewhile the central portion of the guide member forms a space with thecentral portion of the substrate, said peripheral portion of the guidemember being closer to the substrate at said gap as compared to thedistance of said central portion of the guide member from said substrateat said space, and introducing a solvent for said coated film into saidgap while rotating said guide member and said substrate together about asubstantially central axis which keeps the solvent confined to said gapby surface tension of the solvent and achieves dissolution of said filmat said peripheral portion of the substrate while said film at saidcentral portion of the substrate is not contacted by said solvent.